Coating method, coating apparatus and recording medium

ABSTRACT

A coating method includes supplying a film forming liquid onto a center of a front surface of a substrate from a nozzle in a state that a distance between the front surface and the nozzle is maintained at a coating distance; rotating the substrate at a first rotation speed in a period during which the film forming liquid is supplied onto the front surface, to allow the film forming liquid to be diffused toward an edge of the substrate from an outer periphery of the nozzle; and rotating the substrate at a second rotation speed after the supplying of the film forming liquid is stopped, to allow the film forming liquid to be further diffused. The coating distance is set to allow the film forming liquid to be kept between the nozzle and the front surface when a discharge of the film forming liquid is stopped.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application No.2019-089243 filed on May 9, 2019, the entire disclosure of which isincorporated herein by reference.

TECHNICAL FIELD

The various aspects and embodiments described herein pertain generallyto a coating method, a coating apparatus and a recording medium.

BACKGROUND

Patent Document 1 describes a coating apparatus including a substrateholder configured to hold a substrate; a rotator configured to rotatethe substrate held by the substrate holder; a supply configured tosupply a coating liquid onto a front surface of the substrate held bythe substrate holder; and an air flow control plate provided at a presetposition above the substrate held by the substrate holder and configuredto locally change, at a certain position, an air flow above thesubstrate being rotated by the rotator.

-   Patent Document 1: Japanese Patent Laid-open Publication No.    2012-238838

SUMMARY

In one exemplary embodiment, a coating method includes supplying a filmforming liquid onto a center of a front surface of a substrate from anozzle in a state that a distance between the front surface of thesubstrate and the nozzle is maintained at a coating distance; rotatingthe substrate at a first rotation speed around an axis, which passesthrough the center of the front surface of the substrate, in a periodduring which the film forming liquid is supplied onto the front surfaceof the substrate from the nozzle, to allow the film forming liquid to bediffused toward an edge of the substrate from an outer periphery of thenozzle by a centrifugal force; and rotating the substrate at a secondrotation speed around the axis after the supplying of the film formingliquid onto the front surface of the substrate from the nozzle isstopped, to allow the film forming liquid to be further diffused by acentrifugal force. The coating distance is set to allow the film formingliquid to be kept between the nozzle and the front surface of thesubstrate when a discharge of the film forming liquid from the nozzle isstopped.

The foregoing summary is illustrative only and is not intended to be anyway limiting. In addition to the illustrative aspects, embodiments, andfeatures described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description that follows, embodiments are described asillustrations only since various changes and modifications will becomeapparent to those skilled in the art from the following detaileddescription. The use of the same reference numbers in different figuresindicates similar or identical items.

FIG. 1 is a diagram illustrating a schematic configuration of a liquidprocessing system;

FIG. 2 is a diagram illustrating a schematic configuration of a coatingunit;

FIG. 3 is a block diagram illustrating a functional configuration of acontroller;

FIG. 4 is a block diagram illustrating a hardware configuration of thecontroller;

FIG. 5 is a flowchart illustrating a coating sequence;

FIG. 6 is a flowchart illustrating the coating sequence;

FIG. 7 is a flowchart illustrating the coating sequence;

FIG. 8A to FIG. 8C are schematic diagrams illustrating states of a waferwhen a pre-wet liquid is coated;

FIG. 9A and FIG. 9B are schematic diagrams illustrating states of thewafer when cooling is begun and a cover is closed;

FIG. 10A to FIG. 10C are schematic diagrams illustrating states of thewafer during a supply of a resist liquid; and

FIG. 11A to FIG. 11C are schematic diagrams illustrating states of thewafer when the supply of the resist liquid is stopped and the resistliquid is diffused.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part of the description. In thedrawings, similar symbols typically identify similar components, unlesscontext dictates otherwise. Furthermore, unless otherwise noted, thedescription of each successive drawing may reference features from oneor more of the previous drawings to provide clearer context and a moresubstantive explanation of the current exemplary embodiment. Still, theexemplary embodiments described in the detailed description, drawings,and claims are not meant to be limiting. Other embodiments may beutilized, and other changes may be made, without departing from thespirit or scope of the subject matter presented herein. It will bereadily understood that the aspects of the present disclosure, asgenerally described herein and illustrated in the drawings, may bearranged, substituted, combined, separated, and designed in a widevariety of different configurations, all of which are explicitlycontemplated herein.

[Substrate Processing System]

A substrate processing system 1 is a system configured to performformation of a photosensitive film on a substrate, exposure of thephotosensitive film and development of the photosensitive film. Thesubstrate as a processing target object is, for example, a semiconductorwafer W. The photosensitive film is, by way of example, a resist film.The substrate processing system 1 includes a coating and developingapparatus 2 and an exposure apparatus 3. The exposure apparatus 3 isconfigured to perform an exposure processing of the resist film(photosensitive film) formed on the wafer W (substrate). To elaborate,the exposure apparatus 3 irradiates an energy beam to an exposure targetportion of the resist film by an immersion lithography or the like. Thecoating and developing apparatus 2 is configured to perform a processingof forming the resist film on a front surface of the wafer W (substrate)prior to the exposure processing by the exposure apparatus 3, and thento perform a developing processing on the resist film after the exposureprocessing.

<Coating Apparatus>

Hereinafter, a configuration of the coating and developing apparatus 2as an example of a coating apparatus will be described. As depicted inFIG. 1, the coating and developing apparatus 2 is equipped with acarrier block 4, a processing block 5, an interface block 6 and acontroller 100.

The carrier block 4 is configured to carry a wafer W into/from thecoating and developing apparatus 2. For example, the carrier block 4 isconfigured to support a plurality of carriers C for wafers W andincorporates therein a delivery arm A1. Each carrier C accommodatestherein, for example, a multiple number of circular wafers W. Thedelivery arm A1 is configured to take out a wafer W from the carrier C,hand the wafer W over to the processing block 5, receive the wafer Wfrom the processing block 5 and return the wafer W back into the carrierC.

The processing block 5 includes multiple processing modules 11, 12, 13and 14. Each of the processing modules 11, 12 and 13 incorporatescoating units U1, heat treatment units U2 and a transfer arm A3configured to transfer the wafer W into these units.

The processing module 11 is configured to form a bottom film on thesurface of the wafer W by the coating unit U1 and the heat treatmentunit U2. The coating unit U1 of the processing module 11 is configuredto coat a film forming liquid for forming the bottom film on the waferW. The heat treatment unit U2 of the processing module 11 is configuredto perform various kinds of heat treatments required to form the bottomfilm.

The processing module 12 is configured to form a resist film on thebottom film by the coating unit U1 and the heat treatment unit U2. Thecoating unit U1 of the processing module 12 is configured to coat a filmforming liquid for forming a resist film (hereinafter, referred to as“resist liquid”) on the bottom film. The heat treatment unit U2 of theprocessing module 12 is configured to perform various kinds of heattreatments required to form the resist film.

The processing module 13 is configured to form a top film on the resistfilm by the coating unit U1 and the heat treatment unit U2. The coatingunit U1 of the processing module 13 is configured to coat a film formingliquid for forming the top film on the resist film. The heat treatmentunit U2 of the processing module 13 is configured to perform variouskinds of heat treatments required to form the top film.

The processing module 14 incorporates therein developing units U3, heattreatment units U4, and a transfer arm A3 configured to transfer thewafer W into these units.

The processing module 14 is configured to perform a developingprocessing of the exposed resist film by the developing unit U3 and theheat treatment unit U4. The developing unit U3 is configured to performthe developing processing of the resist film by coating a developingliquid on the surface of the exposed wafer W and washing it with a rinseliquid. The heat treatment unit U4 is configured to perform variouskinds of heat treatments required for the developing processing.Specific examples of these heat treatments include a heat treatment(PEB: Post Exposure Bake) performed before the developing processing, aheat treatment (PB: Post Bake) performed after the developingprocessing, and so forth.

Within the processing block 5, a shelf unit U10 is provided at a side ofthe carrier block 4. The shelf unit U10 is partitioned into a multiplenumber of cells arranged in the vertical direction. An elevation arm A7is provided in the vicinity of the shelf unit U10. The elevation arm A7is configured to move the wafer W up and down among the cells of theshelf unit U10.

Within the processing block 5, a shelf unit U11 is provided at a side ofthe interface block 6. The shelf unit U11 is partitioned into multiplecells which are arranged in the vertical direction.

The interface block 6 is configured to deliver the wafer W into/from theexposure apparatus (not shown). By way of example, the interface block 6incorporates a delivery arm A8 and is connected to the exposureapparatus 3. The delivery arm A8 is configured to deliver the wafer Wplaced in the shelf unit U11 to the exposure apparatus 3, and receivesthe wafer W from the exposure apparatus 3 and returns the received waferW back into the shelf unit U11.

The controller 100 controls the coating and developing apparatus 2 toperform a coating and developing processing according to the followingsequence, for example. First, the controller 100 controls the deliveryarm A1 to transfer the wafer W within the carrier C to the shelf unitU10, and controls the elevation arm A7 to place this wafer W in the cellfor the processing module 11.

Then, the controller 100 controls the transfer arm A3 to transfer thewafer W of the shelf unit U10 into the coating unit U1 and the heattreatment unit U2 within the processing module 11, and controls thecoating unit U1 and the heat treatment unit U2 to form the bottom filmon the surface of the wafer W. Thereafter, the controller 100 controlsthe transfer arm A3 to return the wafer W having the bottom film formedthereon back into the shelf unit U10, and then controls the elevationarm A7 to place this wafer W in the cell for the processing module 12.

Subsequently, the controller 100 controls the transfer arm A3 totransfer the wafer W of the shelf unit U10 into the coating unit U1 andthe heat treatment unit U2 within the processing module 12, and controlsthe coating unit U1 and the heat treatment unit U2 to form the resistfilm on the bottom film of the wafer W. Thereafter, the controller 100controls the transfer arm A3 to return the wafer W back into the shelfunit U10, and controls the elevation arm A7 to place this wafer W in thecell for the processing module 13.

Afterwards, the controller 100 controls the transfer arm A3 to transferthe wafer W of the shelf unit U10 to the respective units within theprocessing module 13 and controls the coating unit U1 and the heattreatment unit U2 to form the top film on the resist film of the waferW. Then, the controller 100 controls the transfer arm A3 to transfer thewafer W to the shelf unit U11.

Thereafter, the controller 100 controls the delivery arm A8 to deliverthe wafer W of the shelf unit U11 to the exposure apparatus. Then, thecontroller 100 controls the delivery arm A8 to receive from the exposureapparatus the wafer W on which the exposure processing is alreadyperformed and return the received wafer W in the cell within the shieldunit U11 for the processing module 14.

Thereafter, the controller 100 controls the transfer arm A3 to transferthe wafer W of the shelf unit U11 into the respective units within theprocessing module 14, and controls the developing unit U3 and the heattreatment unit U4 to perform the developing processing on the resistfilm of the wafer W. Then, the controller 100 controls the transfer armA3 to return the wafer W to the shelf unit U10, and controls theelevation arm A7 and the delivery arm A1 to return this wafer W backinto the carrier C. Then, the coating and developing processing isended.

A specific configuration of the substrate processing apparatus is notlimited to the above-described configuration of the coating anddeveloping apparatus 2. The substrate processing apparatus may beimplemented by any of various types of apparatuses as long as it isequipped with the coating unit U1 and the controller 100 configured tocontrol this coating unit U1.

<Coating Unit>

Now, a configuration of the coating unit U1 provided in the processingmodule 12 will be elaborated. As depicted in FIG. 2, the coating unit U1includes a rotating holder 20, liquid supplies 30 and 40, nozzletransfer devices 50 and 60, a cup 70, an opening/closing unit 80 and acooler 90.

The rotating holder 20 is configured to hold the wafer W from a rearsurface Wb side thereof and rotate the wafer W. By way of example, therotating holder 20 is equipped with a holder 21 and a rotation driver22. The holder 21 is configured to support a central portion (a portionincluding a center) of the wafer W, which is horizontally placed thereonwith a front surface Wa facing upwards, from the rear surface Wb sidethereof, and configured to hold the wafer W by, for example, vacuumattraction. The rotation driver 22 is configured to rotate the holder 21around a vertical axis Ax1, which passes through the center of the waferW, by using, for example, an electric motor as a power source.Accordingly, the wafer W is also rotated.

The liquid supply 30 is configured to supply the resist liquid onto thefront surface Wa of the wafer W held by the holder 21. By way ofexample, the liquid supply 30 supplies the resist liquid having aviscosity equal to or less than 5 cP onto the front surface Wa of thewafer W. By way of non-limiting example, the liquid supply 30 includes anozzle 31, a liquid source 32 and a valve 33. The nozzle 31 isconfigured to discharge the resist liquid downwards. The liquid source32 supplies the resist liquid to the nozzle 31. By way of example, theliquid source 32 includes a tank configured to store the resist liquidtherein, a pump configured to force-feed the resist liquid, and soforth. The valve 33 serves to open/close a flow path for the resistliquid from the liquid source 32 to the nozzle 31. The valve 33 may beconfigured to be capable of adjusting a degree of openness of the flowpath for the resist liquid. With this configuration, a discharge amountof the resist liquid from the nozzle 31 can be adjusted.

The liquid supply 40 is configured to supply a pre-wet liquid onto thefront surface Wa of the wafer W held by the holder 21. By way ofexample, the liquid supply 40 supplies an organic solvent such as athinner onto the front surface Wa of the wafer W. By way of non-limitingexample, the liquid supply 40 includes a nozzle 41, a liquid source 42and a valve 43. The nozzle 41 is configured to discharge the pre-wetliquid downwards. The liquid source 42 supplies the pre-wet liquid tothe nozzle 41. For example, the liquid source 42 includes a tankconfigured to store the pre-wet liquid therein, a pump configured toforce-feed the pre-wet liquid, and so forth. The valve 43 serves toopen/close a flow path for the pre-wet liquid from the liquid source 42to the nozzle 41. The valve 43 may be configured to be capable ofadjusting a degree of openness of the flow path for the pre-wet liquid.With this configuration, a discharge amount of the pre-wet liquid formthe nozzle 41 can be adjusted.

The nozzle transfer device 50 is configured to transfer the nozzle 31 ofthe liquid supply 30. By way of example, the nozzle transfer device 50includes a horizontal transfer unit 51 and an elevating unit 52. Thehorizontal transfer unit 51 is configured to transfer the nozzle 31along a horizontal transfer line by using, for example, an electricmotor as a power source. The elevating unit 52 is configured to move thenozzle 31 up and down by using, for example, an electric motor as apower source.

The nozzle transfer device 60 is configured to transfer the nozzle 41 ofthe liquid supply 40. By way of example, the nozzle transfer device 60includes a horizontal transfer unit 61 and an elevating unit 62. Thehorizontal transfer unit 61 is configured to transfer the nozzle 41along a horizontal transfer line by using, for example, an electricmotor as a power source. The elevating unit 62 is configured to move thenozzle 41 up and down by using, for example, an electric motor as apower source.

The cup 70 is configured to accommodate the wafer W and the holder 21therein and configured to receive various kinds of processing liquids(for example, the resist liquid and the pre-wet liquid) scattered fromthe wafer W. The cup 70 has, at a top portion thereof, an opening 71 forcarry-in/out of the wafer W. Further, the cup 70 has an umbrella-shapedportion 72, a drain portion 73, an exhaust portion 74 and an exhaustvalve 75. The umbrella-shaped portion 72 is provided under the holder 21and guides the various processing liquids scattered from the wafer Wdown to a drain region 70 a at an outer peripheral side within the cup70. The drain portion 73 is provided under the umbrella-shaped portion72 within the drain region 70 a, and the processing liquids guided intothe drain region 70 a by the umbrella-shaped portion 72 is drained to anoutside of the cup 70 through this drain portion 73. The exhaust portion74 is provided under the umbrella-shaped portion 72 within an exhaustregion 70 b at an inner side than the drain region 70 a, and a gaswithin the cup 70 is exhausted to the outside of the cup 70 through thisexhaust portion 74. The exhaust valve 75 is configured to open/close anexhaust path for the gas through the exhaust portion 74.

The opening/closing unit 80 is configured to open/close the opening 71of the cup 70. By way of example, the opening/closing unit 80 includes acover member 81 and an opening/closing driver 82. The cover member 81 isa plate-shaped member configured to close the opening 71. The covermember 81 has a nozzle insertion opening 83 for allowing the nozzle 31to be inserted therethrough, and this nozzle insertion opening 83 isprovided at a position facing the central portion (including the center)of the front surface Wa of the wafer W (held by the holder 21) when thecover member 81 closes the opening 71. The opening/closing driver 82 isconfigured to move the cover member 81 between a closing position wherethe cover member 81 closes the opening 71 and an opening position wherethe cover member 81 opens the opening 71 by using, for example, anelectric motor as a power source.

The cooler 90 is configured to cool at least a part of the wafer W heldby the holder 21. By way of example, the cooler 90 cools an annularregion of the wafer W at an outer side than a region of the wafer W heldby the holder 21. For example, the cooler 90 is configured to supply acooling liquid to the rear surface Wb of the wafer W. As an example, thecooler 90 includes a nozzle 91, a liquid source 92 and a valve 93. Thecooling liquid may be, by way of example, but not limitation, a volatilesolvent such as isopropyl alcohol (IPA), a thinner or acetone.

The nozzle 91 is provided near the holder 21 and discharges the coolingliquid toward the rear surface Wb of the wafer W held by the holder 21.If the cooling liquid is supplied to the rear surface Wb from the nozzle91 while the wafer W is being rotated by the rotating holder 20, theaforementioned annular region of the wafer W is cooled. A dischargingdirection of the cooling liquid from the nozzle 91 may be inclinedtoward an edge We of the wafer W. The liquid source 92 is configured tosupply the cooling liquid to the nozzle 91. By way of example, theliquid source 92 includes a tank configured to store the cooling liquidtherein, a pump configured to force-feed the cooling liquid, and soforth. The valve 93 serves to open/close a flow path for the coolingliquid from the liquid source 92 into the nozzle 91. The valve 93 may beconfigured to be capable of adjusting a degree of openness of the flowpath for the cooling liquid. With this configuration, a discharge amountof the cooling liquid from the nozzle 91 can be adjusted.

Furthermore, the method of cooling the wafer W is not necessarilylimited to supplying the cooling liquid to the wafer W. By way ofexample, the cooler 90 may be configured to discharge a cooling gas tothe rear surface Wb of the wafer W from the nozzle 91. Further, thecooler 90 may be configured to cool the wafer W indirectly by coolingthe gas within the cup 70.

The coating unit U1 having the above-described configuration iscontrolled by the controller 100. The controller 100 may be configuredto control the liquid supply 30 and the nozzle transfer device 50 tosupply the resist liquid onto the center of the front surface Wa of thewafer W from the nozzle 31 in a state that a distance between the frontsurface Wa of the wafer W and the nozzle 31 is maintained at a presetdistance for coating (hereinafter, referred to as “coating distance”);and control the rotating holder 20 to rotate the wafer W at a firstrotation speed around the axis Ax1 passing the center of the frontsurface Wa of the wafer W in a period during which the resist liquid issupplied onto the front surface Wa of the wafer W from the nozzle 31,thus allowing the resist liquid to be diffused to the edge We of thewafer W from an outer periphery of the nozzle 31 by a centrifugal force,and to rotate the wafer W at a second rotation speed around the axis Ax1after the supply of the resist liquid onto the front surface Wa of thewafer W from the nozzle 31 is stopped, thus allowing the resist liquidto be further diffused by a centrifugal force.

As shown in FIG. 3, the controller 100 includes, as functionalcomponents (hereinafter, referred to as “functional modules”), a liquidsupply controller 111, a liquid supply controller 112, a nozzle transfercontroller 113, a nozzle transfer controller 114, a rotation controller115, an opening/closing controller 116 and a cooling controller 117.

The liquid supply controller 111 controls the liquid supply 30 to supplythe resist liquid onto the center of the front wafer Wa of the wafer Wfrom the nozzle 31 in the state that the distance between the frontsurface Wa of the wafer W and the nozzle 31 is maintained at theaforementioned coating distance. The coating distance is set to keep theresist liquid between the nozzle 31 and the front surface Wa of thewafer W when the discharge of the resist liquid from the nozzle 31 isstopped. Here, the keeping the resist liquid between the nozzle 31 andthe front surface Wa of the wafer W means allowing the resist liquid tostay between a lower end surface 31 a of the nozzle 31 and the frontsurface Wa of the wafer Win a state that both the lower end surface 31 aand the front surface Wa of the wafer W are in contact with the resistliquid. The coating distance is equal to or less than three times aninner diameter ID1 of the nozzle 31. The coating distance may be equalto or less than twice the inner diameter ID1 of the nozzle 31.

If the coating distance is equal to or less than a thickness of a liquidfilm of the resist liquid (that is, a liquid film formed on the frontsurface Wa as a result of the supply of the resist liquid), the resistliquid is kept between the nozzle 31 and the front surface Wa even whenthe discharge of the resist liquid from the nozzle 31 is stopped. Evenif the coating distance is larger than the thickness of the liquid filmof the resist liquid, the resist liquid can still be kept between thelower end surface 31 a and the front surface Wa since the coatingdistance is set such that an adhesive strength between the lower endsurface 31 a and the resist liquid becomes equal to or larger than aweight of the resist liquid. If the coating distance is larger than thethickness of the liquid film of the resist liquid, that is, if the lowerend surface 31 a is located higher than the liquid film, the resistliquid may be more easily diffused toward an outer periphery of thewafer W from a portion of the wafer W to which the resist liquidadheres. Furthermore, since a region of the lower end surface 31 a towhich the resist liquid adheres is suppressed to be small, it becomesdifficult for the resist liquid to remain at the lower end surface 31 awhen the supply of the resist liquid is stopped and when the resistliquid is suctioned (sucked back) into the nozzle 31 afterwards.

The coating distance may be set to allow a liquid column of the resistliquid formed between the lower end surface 31 a and the front surfaceWa to have a narrow portion. That is, the coating distance may be set toallow the resist liquid staying between the lower end surface 31 a andthe front surface Wa to have a column shape which is gradually enlargedafter being once narrowed from the lower end surface 31 a side towardthe front surface Wa. Thus, as compared to the case where the coatingdistance is equal to or less than the film thickness of the liquid film,an adhesion region of the resist liquid with respect to the liquid filmis reduced. In this case, the adhesion region of the resist film withrespect to the liquid film is further reduced.

On the lower end surface 31 a of the nozzle 31, a width of an annularportion surrounding the opening may be less than the inner diameter ID1of the opening. Most of the lower end surface 31 a may not be parallelto the front surface Wa. By way of example, the lower end surface 31 amay be inclined to be distanced farther from the front surface Wa as itgoes toward the outer periphery thereof. Further, the lower end surface31 a may be inclined to be distanced farther from the front surface Waas it goes toward an inner periphery thereof. Furthermore, the lower endsurface 31 a may be inclined to be distanced farther from the frontsurface Wa as it goes both outwards and inwards. That is, a portion ofthe lower end surface 31 a between the outer periphery and the innerperiphery may be protruded toward the front surface Wa. Further, theportion of the lower end surface 31 a between the outer periphery andthe inner periphery may be formed as a curved surface protruding towardthe front surface Wa. In any of these cases, the resist liquid adheringto the lower end surface 31 a may be easily distanced away from thelower end surface 31 a, so that it becomes difficult for the resistliquid to remain at the lower end surface 31 a.

The liquid supply controller 111 may control the liquid supply 30 tostop the discharge of the resist liquid from the nozzle 31 before theresist liquid reaches the edge We of the wafer W. A timing when theliquid supply controller 111 stops the discharge of the resist liquidfrom the nozzle 31 may be set to allow the resist liquid to arrive at aposition on the wafer W 0.3 times to 1.0 times (or 0.4 times or 0.8times) the radius of the wafer W from the center of the wafer W at thecorresponding time. The timing when the liquid supply controller 111stops the discharge of the resist liquid from the nozzle 31 may be setto allow the resist liquid to reach the aforementioned annular region(cooling target region) at the corresponding time. When the resistliquid is supplied onto the front surface Wa of the wafer W from thenozzle 31, the liquid supply controller 111 may control the liquidsupply 30 to discharge the resist liquid having the viscosity equal toor less than 5 cP from the nozzle 31 at a flow rate of 0.2 cc persecond.

The liquid supply controller 112 may control the liquid supply 40 tosupply the pre-wet liquid onto the front surface Wa of the wafer Wbefore the liquid supply controller 111 begins the supply of the resistliquid onto the front surface Wa of the wafer W from the nozzle 31.

The nozzle transfer controller 113 controls the nozzle transfer device60 to place the nozzle 41 at a position above the center of the wafer Wby using the horizontal transfer unit 61 before the pre-wet liquid issupplied onto the front surface Wa of the wafer W from the nozzle 41.Then, the nozzle transfer controller 113 controls the nozzle transferdevice 60 to move the nozzle 41 close to the front surface Wa by usingthe elevating unit 62. After the pre-wet liquid is supplied onto thefront surface Wa of the wafer W from the nozzle 41, the nozzle transfercontroller 113 controls the nozzle transfer device 60 to move the nozzle41 away from the front surface Wa by using the elevating unit 62.Thereafter, the nozzle transfer controller 113 controls the nozzletransfer device 60 to retreat the nozzle 41 from above the wafer W byusing the horizontal transfer unit 61.

The nozzle transfer controller 114 controls the nozzle transfer device50 to locate the nozzle 31 at the position above the center of the waferW by using the horizontal transfer unit 51 before the supply of theresist liquid onto the front surface Wa is performed and after thepre-wet liquid is coated on the front surface Wa of the wafer W. Then,the nozzle transfer controller 114 controls the nozzle transfer device50 to move the nozzle 31 close to the front surface Wa by using theelevating unit 52 until the distance between the front surface Wa andthe nozzle 31 becomes the aforementioned coating distance. Then, afterthe resist liquid is supplied onto the front surface Wa of the wafer Wfrom the nozzle 31, the nozzle transfer controller 114 controls thenozzle transfer device 50 to move the nozzle 31 away from the frontsurface Wa by using the elevating unit 52. Thereafter, the nozzletransfer controller 114 controls the nozzle transfer device 50 toretreat the nozzle 31 from above the wafer W by using the horizontaltransfer unit 51.

In the period during which the resist liquid is supplied onto the frontsurface Wa of the wafer W from the nozzle 31, the rotation controller115 controls the rotating holder 20 to rotate the wafer W at the firstrotation speed so that the resist liquid is diffused toward the edge Wcof the wafer W from the outer periphery of the nozzle 31 by thecentrifugal force. The first rotation speed is set such that the supplyof the resist liquid, which is discharged from the nozzle 31 at the flowrate equal to or less than 0.2 cc per second, onto the edge Wc does notstopped. By way of example, the first rotation speed may be 1000 rpm to2000 rpm, 1200 rpm to 1800 rpm, or 1400 rpm to 1600 rpm. After thesupply of the resist liquid onto the front surface Wa of the wafer Wfrom the nozzle 31 is stopped, the rotation controller 115 controls therotating holder 20 to rotate the wafer W at the second rotation speed sothat the resist liquid is further diffused by the centrifugal force. Thesecond rotation speed is equal or larger than the first rotation speed.By way of non-limiting example, the second rotation speed may be 1300rpm to 2300 rpm, 1500 rpm to 2100 rpm, or 1700 rpm to 1900 rpm.

The rotation controller 115 may control the rotating holder 20 todecrease the rotation speed of the wafer W to a third rotation speedlower than the first rotation speed before the nozzle 31 is moved awayfrom the front surface Wa and after the discharge of the resist liquidfrom the nozzle 31 is stopped. In this case, after the nozzle 31 ismoved away from the front surface Wa, the rotation controller 115controls the rotating holder 20 to increase the rotation speed of thewafer W from the third rotation speed to the second rotation speed. Byway of non-limiting example, the third rotation speed may be 0 rpm to200 rpm, 50 rpm to 150 rpm, or 80 rpm to 120 rpm. With thisconfiguration in which the rotation speed of the wafer W is decreasedwhen the nozzle 31 is moved away from the front surface Wa, the nozzle31 can be raised while a flow (expansion) of the resist liquid toward anouter periphery of the front surface Wa is suppressed. Accordingly,falling of the liquid or unnecessary supplying of the liquid due to acut-off of the liquid can be suppressed.

The rotation controller 115 may decrease the rotation speed of the waferW by the rotating holder 20 to the third rotation speed before thedischarge of the resist liquid from the nozzle 31 is stopped, and maymaintain the rotation speed of the wafer W at the third rotation speeduntil the nozzle 31 is distanced away from the wafer W. In this case,the stopping of the discharge of the resist liquid and the raising ofthe nozzle 31 can be performed in the state that the flow (expansion) ofthe resist liquid toward the outer periphery of the front surface Wa andthe rotation speed of the wafer W is suppressed. Thus, the falling ofthe liquid or the unnecessary supplying of the liquid due to a cut-offof the liquid can be further suppressed.

In addition, the aforementioned coating distance may be set to besmaller than a liquid droplet of the resist liquid that can be formed bythe nozzle 31. In this case, when the nozzle 31 is raised, the distancebetween the front surface Wa and the lower end surface 31 a is changedfrom a state where it is smaller than the liquid droplet into a statewhere it is larger than the liquid droplet. That is, the distancebetween the front surface Wa and the lower end surface 31 a is changedfrom a distance where the liquid droplet cannot be formed into adistance where the liquid droplet can be formed. In this case, theeffect of suppressing the falling of the liquid or the unnecessarysupplying of the liquid becomes more conspicuous.

In a period during which the pre-wet liquid is supplied onto the frontsurface Wa of the wafer W from the nozzle 41, the rotation controller115 rotates the wafer W at a fourth rotation speed which allows thepre-wet liquid to stay on the front surface Wa. The fourth rotationspeed may be equal to or less than the third rotation speed. By way ofexample, the fourth rotation speed may be 0 rpm to 100 rpm, 10 rpm to 70rpm, or 20 rpm to 40 rpm.

Further, the rotation controller 115 controls the rotating holder 20 torotate the wafer W at a fifth rotation speed such that the pre-wetliquid supplied onto the front surface Wa of the wafer W from the nozzle41 is diffused toward the edge We of the wafer W by the centrifugalforce and a surplus of the pre-wet liquid is scattered from the edge ofthe wafer W. The fifth rotation speed may be equal to or larger than thesecond rotation speed. By way of example, the fifth rotation speed maybe 1000 rpm to 3000 rpm, 1500 rpm to 2500 rpm, or 1800 rpm to 2200 rpm.

The opening/closing controller 116 controls the opening/closing unit 80to locate the cover member 81 configured to suppress volatilization of asolvent of the resist liquid at a position facing the front surface Wabefore the supply of the resist liquid onto the front surface Wa of thewafer W from the nozzle 31 is stopped. By way of example, theopening/closing controller 116 controls the opening/closing unit 80 tomove the cover member 81 to the aforementioned closing position by usingthe opening/closing driver 82 before the supply of the resist liquidonto the front surface Wa of the wafer W from the nozzle 31 is stopped.Further, the opening/closing controller 116 closes the exhaust valve 75at the same time when the opening/closing unit 80 moves the cover member81 to the closing position.

The opening/closing controller 116 controls the opening/closing unit 80to remove the cover member 81 from the position facing the front surfaceWa before the rotation of the wafer W at the second rotation speed iscompleted. By way of example, the opening/closing controller 116controls the opening/closing unit 80 to move the cover member 81 fromthe closing position to the opening position by using theopening/closing driver 82 at a preset timing prior to the completion ofthe rotation of the wafer W at the second rotation speed. Furthermore,the opening/closing controller 116 opens the exhaust valve 75 at thesame time when the opening/closing unit 80 moves the cover member to theopening position. Here, the preset timing may be set such that a periodbetween this preset timing and a timing when the supply of the resistliquid onto the front surface Wa of the wafer W from the nozzle 31 isstopped is shorter than a period between this preset timing and a timingwhen the rotation of the wafer W at the second rotation speed iscompleted. This preset timing may be set to be a time after the supplyof the resist liquid onto the front surface Wa of the wafer W from thenozzle 31 is stopped.

The cooling controller 117 controls the cooler 90 to cool the wafer W inthe period during which the resist liquid is supplied onto the frontsurface Wa of the wafer W from the nozzle 31. By way of example, thecooling controller 117 controls the cooler 90 to supply the coolingliquid to the rear surface Wb of the wafer W from the nozzle 91 in theperiod during which the resist liquid is supplied onto the front surfaceWa of the wafer W from the nozzle 31. As a result, the aforementionedannular region of the wafer W is cooled. The cooling controller 117controls the cooler 90 to stop the cooling of the wafer W before therotation of the wafer W at the second rotation speed is completed. Thecooling controller 117 controls the cooler 90 to stop the discharge ofthe cooling liquid from the nozzle 91 at a predetermined timing beforethe rotation of the wafer W at the second rotation speed is completed.Here, the predetermined timing may be set such that a period betweenthis predetermined timing and the timing when the supply of the resistliquid onto the front surface Wa of the wafer W from the nozzle 31 isstopped is shorter than a period between this predetermined timing andthe timing when the rotation of the wafer W at the second rotation speedis completed. This predetermined timing may be set to be a time afterthe supply of the resist liquid onto the front surface Wa of the wafer Wfrom the nozzle 31 is stopped. A cooling effect for the wafer W iscontinued during a certain period even after the cooling of the wafer Wby the cooler 90 is stopped. In consideration of this, the predeterminedtiming may be set to be a time before the supply of the resist liquidonto the front surface Wa of the wafer W from the nozzle 31 is stopped.

The controller 100 is composed of, by way of example, one or morecontrol computers. For example, the controller 100 has a circuit 120shown in FIG. 4. The circuit 120 is equipped with one or more processors121, a memory 122, a storage 123, an input/output port 124 and a timer125. The storage 123 has a computer-readable recording medium such as,but not limited, a hard disk. The storage 123 stores therein programsthat cause the controller 100 to control the liquid supply 30 and thenozzle transfer device 50 to supply the resist liquid onto the center ofthe front surface Wa of the wafer W from the nozzle 31 in the state thatthe distance between the front surface Wa of the wafer W and the nozzle31 is maintained at the preset coating distance; and control therotating holder 20 to rotate the wafer W at the first rotation speedaround the axis Ax1 passing through the center of the front surface Waof the wafer W in the period during which the resist liquid is suppliedonto the front surface Wa of the wafer W from the nozzle 31, thusallowing the resist liquid to be diffused to the edge We of the wafer Wfrom the outer periphery of the nozzle 31 by the centrifugal force, androtate the wafer W around the axis Ax1 at the second rotation speedafter the supply of the resist liquid onto the front surface Wa of thewafer W from the nozzle 31 is stopped, thus allowing the resist liquidto be further diffused by the centrifugal force. By way of example, thestorage 123 may store therein programs for constituting theabove-described individual functional modules of the controller 100 bythe controller 100.

The memory 122 is configured to temporarily store thereon the programsloaded form the recording medium of the storage 123 and operationresults by the processor 121. The processor 121 executes the programs incooperation with the memory 122, thus constituting the above-describedindividual functional modules. The input/output port 124 is configuredto perform an input/output of an electric signal among the rotatingholder 20, the liquid supply 30, the liquid supply 40, the nozzletransfer device 50, the nozzle transfer device 60, the exhaust valve 75,the opening/closing valve 80 and the cooler 90 in response to aninstruction from the processor 121. The timer 125 is configured tomeasure an elapsed time by counting, for example, a reference pulse of apreset cycle.

Further, the hardware configuration of the controller 100 is not limitedto constituting the individual functional modules by the programs. Byway of example, each functional module of the controller 100 may beimplemented by a dedicated logical circuit or an ASIC (ApplicationSpecific Integrated Circuit) which is an integration of the logicalcircuits.

[Coating Sequence]

Now, a coating sequence performed by the coating unit U1 will beelaborated as an example of a coating method. This coating sequenceincludes: supplying the resist liquid onto the center of the frontsurface Wa of the wafer W from the nozzle 31 in the state that thedistance between the front surface Wa and the nozzle 31 is maintained atthe coating distance; rotating the wafer W at the first rotation speedaround the axis Ax1, which passes through the center of the frontsurface Wa, in the period during which the resist liquid is suppliedonto the front surface Wa from the nozzle 31, thus allowing the resistliquid to be diffused to the edge We of the wafer W from the outerperiphery of the nozzle 31 by the centrifugal force; and rotating thewafer W around the axis Ax1 at the second rotation speed after thesupply of the resist liquid onto the front surface Wa from the nozzle 31is sopped, thus allowing the resist liquid to be further diffused by thecentrifugal force.

By way of example, the controller 100 first performs processes S01, S02and S03, as shown in FIG. 5. In the process S01, the nozzle transfercontroller 113 controls the nozzle transfer device 60 to locate thenozzle 41 at the position above the center of the wafer W by using thehorizontal transfer unit 61. Then, the nozzle transfer controller 113controls the nozzle transfer device 60 to move the nozzle 41 close tothe front surface Wa by using the elevating unit 62 (see FIG. 8A). Inthe process S02, the rotation controller 115 controls the rotatingholder 20 to start rotating the wafer W at the fourth rotation speed. Inthe process S03, the liquid supply controller 112 controls the liquidsupply 40 to supply a preset amount of the pre-wet liquid onto the frontsurface Wa of the wafer W (see FIG. 8B).

Subsequently, the controller 100 performs processes S04, S05 and S06. Inthe process S04, the rotation controller 115 controls the rotatingholder 20 to increase the rotation speed of the wafer W from the fourthrotation speed to the fifth rotation speed. Accordingly, the pre-wetliquid supplied onto the front surface Wa of the wafer W from the nozzle41 is diffused to the edge We of the wafer W by the centrifugal force,and the surplus of the pre-wet liquid is scattered from the edge of thewafer W (see FIG. 8C). In the process S05, the nozzle transfercontroller 113 controls the nozzle transfer device 60 to move the nozzle41 away from the front surface Wa by using the elevating unit 62 andretreat the nozzle 41 from above the wafer W by using the horizontaltransfer unit 61. In the process S06, the rotation controller 115 standsby until a predetermined time elapses from a timing when the rotation ofthe wafer W at the fifth rotation speed is begun. Here, thepredetermined time is set through a previous test or simulation to allowthe surplus of the pre-wet liquid to be scattered sufficiently.

Thereafter, the controller 100 performs processes S11, S12 and S13, asshown in FIG. 6. In the process S11, the rotation controller 115controls the rotating holder 20 to decrease the rotation speed of thewafer W from the fifth rotation speed to the first rotation speed. Inthe process S12, the cooling controller 117 controls the cooler 90 tostart supplying the cooling liquid to the rear surface Wb of the wafer Wfrom the nozzle 91 (see FIG. 9A). In the process S13, theopening/closing controller 116 controls the opening/closing unit 80 tomove the cover member 81 to the aforementioned closing position (theposition facing the front surface Wa) by using the opening/closingdriver 82 (see FIG. 9B). Further, in the process S13, theopening/closing controller 116 closes the exhaust valve 75.

Subsequently, the controller 100 performs processes S14, S15, S16 andS17. In the process S14, the nozzle transfer controller 114 controls thenozzle transfer device 50 to place the nozzle 31 at the position abovethe center of the wafer W by using the horizontal transfer unit 51 (seeFIG. 10A). In the process S15, the nozzle transfer controller 114controls the nozzle transfer device 50 to move the nozzle 31 close tothe front surface Wa by using the elevating unit 52 until the distancebetween the front surface Wa and the nozzle 31 becomes theaforementioned coating distance (see FIG. 10B). In the process S16, theliquid supply controller 111 controls the liquid supply 30 to start thesupply of the resist liquid onto the front surface Wa of the wafer Wfrom the nozzle 31 in the state that the distance between the frontsurface Wa and the nozzle 31 is maintained at the aforementioned coatingdistance (see FIG. 10C). In the process S17, the liquid supplycontroller 111 stands by until a predetermined time elapses from thetiming when the discharge of the resist liquid from the nozzle 31 isbegun. The predetermined time is set through a previous test orsimulation to supply the resist liquid in a sufficient amount to achievea target film thickness of the resist film.

Then, the controller 100 performs processes S21, S22, S23 and S24 asshown in FIG. 7. In the process S21, the rotation controller 115controls the rotating holder 20 to decrease the rotation speed of thewafer W from the first rotation speed to the third rotation speed. Inthe process S22, the liquid supply controller 111 controls the liquidsupply 30 to stop the discharge of the resist liquid from the nozzle 31.In the process S23, the nozzle transfer controller 114 controls thenozzle transfer device 50 to move the nozzle 31 away from the frontsurface Wa by using the elevating unit 52 (see FIG. 11A). In the processS24, the nozzle transfer controller 114 controls the nozzle transferdevice 50 to retreat the nozzle 31 from above the wafer W by using thehorizontal transfer unit 51.

Subsequently, the controller 100 performs processes S25 and S26. In theprocess S25, the rotation controller 115 controls the rotating holder 20to increase the rotation speed of the wafer W from the third rotationspeed to the second rotation speed. Accordingly, the resist liquid onthe front surface Wa is further diffused to the edge Wc, and the surplusof the resist liquid is scattered off the front surface Wa (see FIG.11B). In the process S26, the rotation controller 115 stands by until apredetermined time elapses from the timing when the rotation of thewafer W at the second rotation speed is begun. This predetermined timeis set through a previous test or simulation to improve uniformity ofthe film thickness of the resist film.

Afterwards, the controller 100 performs processes S27, S28, S29 and S31.In the process S27, the cooling controller 117 controls the cooler 90 tostop the supply of the cooling liquid to the rear surface Wb of thewafer W from the nozzle 91. In the process S28, the opening/closingcontroller 116 controls the opening/closing unit 80 to move the covermember 81 to the opening position from the closing position by using theopening/closing driver 82 (see FIG. 11C). Further, in the process S28,the opening/closing controller 116 opens the exhaust valve 75. In theprocess S29, the rotation controller 115 stands by until a predeterminedtime elapses from the timing when the rotation of the wafer W at thesecond rotation speed is begun. In the meanwhile, the diffusion of theresist liquid toward the edge Wc is continued. The predetermined time isset through a previous test or simulation to improve the uniformity ofthe film thickness of the resist film. In the process S31, the rotationcontroller 115 controls the rotating holder 20 to stop the rotation ofthe wafer W. Through these processes, the coating sequence is completed.

Effects of Present Exemplary Embodiment

As described above, the coating method according to the presentexemplary embodiment includes: supplying the resist liquid onto thecenter of the front surface Wa of the wafer W from the nozzle 31 in thestate that the distance between the front surface Wa of the wafer W andthe nozzle 31 is maintained at the coating distance; rotating the waferW at the first rotation speed around the axis Ax1, which passes throughthe center of the front surface Wa of the wafer W, in the period duringwhich the resist liquid is supplied onto the front surface Wa of thewafer W from the nozzle 31, thus allowing the resist liquid to bediffused to the edge Wc of the wafer W from the outer periphery of thenozzle 31 by the centrifugal force; and rotating the wafer W around theaxis Ax1 at the second rotation speed after the supply of the resistliquid onto the front surface Wa of the wafer W from the nozzle 31 issopped, thus allowing the resist liquid to be further diffused by thecentrifugal force. The coating distance is set to allow the resistliquid to be kept between the nozzle 31 and the front surface Wa of thewafer W when the discharge of the resist liquid from the nozzle 31 isstopped.

Drying of the resist liquid progresses during a period until the resistliquid reaches the edge Wc of the wafer W after being discharged fromthe nozzle 31. If the drying of the resist liquid progresses up to alevel where fluidity is substantially reduced before the resist liquidreaches the edge Wc of the wafer W, uniformity of the film thickness ofthe film formed by the coating of the resist liquid may be degraded. Byway of example, since the resist liquid may not be sufficiently diffusedto the edge Wc of the wafer W, the film thickness at the peripheralportion of the wafer W may become excessively small. Meanwhile, the filmthickness may become excessively large between the center of the wafer Wand the edge Wc thereof. As a resolution, by supplying the resist liquidin the state that the nozzle 31 is placed close to the wafer W with theaforementioned coating distance therebetween (hereinafter, referred toas “proximity coating”), the drying of the resist liquid is suppressedat least until the resist liquid reaches the edge Wc of the wafer W fromthe nozzle 31. Therefore, the reduction of the fluidity of the resistliquid before the arrival of the resist liquid at the edge Wc of thewafer W can be suppressed, so that the uniformity of the film thicknesscan be improved.

The coating method may further include: coating the pre-wet liquid onthe front surface Wa of the wafer W before the resist liquid is suppliedonto the front surface Wa of the wafer W from the nozzle 31; and, afterthe coating of the pre-wet liquid, moving the nozzle 31 close to thefront surface Wa of the wafer W until the distance between the frontsurface Wa of the wafer W and the nozzle 31 becomes the coatingdistance. In this case, due to the effect of facilitating the diffusionof the resist liquid by the coating of the pre-wet liquid and the effectof further suppressing the reduction of the fluidity of the resistliquid by the proximity coating, the reduction of the fluidity of theresist liquid before the arrival of the resist liquid at the edge Wc ofthe wafer W can be further suppressed. Thus, the uniformity of the filmthickness can be further improved.

The discharge of the resist liquid from the nozzle 31 may be stoppedbefore the resist liquid reaches the edge Wc of the wafer W. In thiscase, it is possible to achieve the uniformity of the film thicknesswhile saving the resist liquid.

When the resist liquid is supplied to the center of the front surface Waof the wafer W from the nozzle 31, the resist liquid having theviscosity equal to or less than 5 cP may be discharged from the nozzle31 at the flow rate of 0.2 cc or less per second. In this case as well,it is possible to achieve the uniformity of the film thickness whilesaving the resist liquid.

The coating distance may be equal to or less than three times the innerdiameter ID1 of the nozzle 31. In this case, the proximity coating canbe carried out more securely. Furthermore, the coating distance may beset to be of a value larger than the film thickness of the liquid film.In such a case, the adhesion region of the resist liquid with respect tothe liquid film can be reduced, so that physical interference betweenthe liquid film and the nozzle 31 can be suppressed. Furthermore, theresist liquid can be suppressed from being left at the nozzle 31 afterthe cut-off of the liquid (rising of the nozzle 31). Therefore, theuniformity of the film thickness can be further improved.

The coating method may further include: placing the cover member 81 forsuppressing volatilization of the solvent of the resist liquid at theposition facing the front surface Wa of the wafer W before the supply ofthe resist liquid onto the front surface Wa of the wafer W from thenozzle 31 is stopped; and removing the cover member 81 from the positionfacing the front surface Wa of the wafer W before the rotation of thewafer W at the second rotation speed is completed. In this case, due tothe effect of suppressing the volatilization of the solvent by the covermember 81 and the effect of further suppressing the reduction of thefluidity of the resist liquid by the proximity coating, the reduction ofthe fluidity of the resist liquid before the arrival of the resistliquid at the edge Wc of the wafer W can be further suppressed.

The coating method may further include: cooling the wafer Win the periodduring which the resist liquid is supplied onto the front surface Wa ofthe wafer W from the nozzle 31; and stopping the cooling of the wafer Wbefore the rotation of the wafer W at the second rotation speed iscompleted. In this case, due to the effect of suppressing thevolatilization of the solvent by the cooling of the wafer W and theeffect of further suppressing the reduction of the fluidity of theresist liquid by the proximity coating, the reduction of the fluidity ofthe resist liquid before the arrival of the resist liquid at the edge Wcof the wafer W can be further suppressed.

The cooling of the wafer W may be stopped at a timing which is set suchthat a period between this timing and the timing when the supply of theresist liquid onto the front surface Wa of the wafer W from the nozzle31 is stopped is shorter than a period between this timing and thetiming when the rotation of the wafer W at the second rotation speed iscompleted. If the cooling of the wafer W is carried out excessivelyduring the rotation of the wafer W at the second rotation speed, theamount of the resist liquid scattered from the wafer W after beingsupplied becomes excessively large, so that the film thickness maybecome excessively small. However, by stopping the cooling of the waferW at the aforementioned timing, the film thickness can be optimized.

When rotating the wafer W, the wafer W may be rotated while being heldby the rotating holder 20 from the rear surface Wb side thereof, andwhen cooling the wafer W, the annular region of the wafer W at the outerside than the region of the wafer W held by the rotating holder 20 maybe cooled. In this case, since a region of the wafer W inside theannular region is not cooled, a more conspicuous effect of the proximitycoating can be obtained.

When cooling the wafer W, the cooling liquid may be supplied to the rearsurface Wb of the wafer W. In this case, a configuration for cooling thewafer W can be simplified.

So far, the exemplary embodiments have been described. However, thepresent disclosure is not necessarily limited to the above-describedexemplary embodiments, and various changes and modifications may be madewithout departing from the scope of the present disclosure. Within arange facing the front surface Wa of the wafer W, the cover member 81may have, around the nozzle insertion opening 83, another opening whichis different from the nozzle insertion opening 83. Hereinafter, thisopening will be referred to as “additional opening”. At a position ofthe front surface Wa facing a region of the additional opening, it isdifficult to suppress volatilization of the solvent. As a result, thefilm thickness of the resist film tends to be thickened at this positionfacing the region of the additional opening. This feature may be used toimprove the uniformity of the film thickness. By way of example, theadditional opening may be formed to correspond to a portion of the waferW where the film thickness is not enough, and the film thickness at thecorresponding portion can be increased. Further, the additional openingmay be moved by the opening/closing driver 82 in the period during whichthe resist liquid is diffused.

The cover member 81 may be moved by the nozzle transfer device 50 alongwith the nozzle 31. In this configuration, the opening/closing driver 82may be omitted. The above-described coating method is also applicable toformation of various other kinds of films (for example, theaforementioned bottom film or top film) other than the resist film. Thesubstrate as the processing target is not limited to the semiconductorwafer, and may be a glass substrate, a mask substrate, a FPD (FlatPatent Display), or the like.

According to the exemplary embodiment, it is possible to provide thecoating method which is advantageous to improve uniformity of a filmthickness.

From the foregoing, it will be appreciated that various embodiments ofthe present disclosure have been described herein for purposes ofillustration, and that various modifications may be made withoutdeparting from the scope and spirit of the present disclosure.Accordingly, the various embodiments disclosed herein are not intendedto be limiting. The scope of the inventive concept is defined by thefollowing claims and their equivalents rather than by the detaileddescription of the exemplary embodiments. It shall be understood thatall modifications and embodiments conceived from the meaning and scopeof the claims and their equivalents are included in the scope of theinventive concept.

We claim:
 1. A coating method, comprising: supplying a film forming liquid onto a center of a front surface of a substrate from a nozzle in a state that a distance between the front surface of the substrate and the nozzle is maintained at a coating distance; rotating the substrate at a first rotation speed around an axis, which passes through the center of the front surface of the substrate, in a period during which the film forming liquid is supplied onto the front surface of the substrate from the nozzle, to allow the film forming liquid to be diffused toward an edge of the substrate from an outer periphery of the nozzle by a centrifugal force; and rotating the substrate at a second rotation speed around the axis after the supplying of the film forming liquid onto the front surface of the substrate from the nozzle is stopped, to allow the film forming liquid to be further diffused by a centrifugal force, wherein the coating distance is set to allow the film forming liquid to be kept between the nozzle and the front surface of the substrate when a discharge of the film forming liquid from the nozzle is stopped.
 2. The coating method of claim 1, further comprising: coating a pre-wet liquid onto the front surface of the substrate before the supplying of the film forming liquid onto the front surface of the substrate from the nozzle; and moving, after the coating of the pre-wet liquid, the nozzle close to the front surface of the substrate until the distance between the front surface of the substrate and the nozzle becomes the coating distance.
 3. The coating method of claim 1, wherein the discharge of the film forming liquid from the nozzle is stopped before the film forming liquid reaches the edge of the substrate.
 4. The coating method of claim 1, wherein when the film forming liquid is supplied onto the center of the front surface of the substrate from the nozzle, the film forming liquid having a viscosity equal to or less than 5 cP is discharged from the nozzle at a flow rate equal to or less than 0.2 cc per second.
 5. The coating method of claim 1, wherein the coating distance is equal to or less than three times an inner diameter of the nozzle.
 6. The coating method of claim 1, further comprising: placing a cover member configured to suppress volatilization of a solvent of the film forming liquid at a position facing the front surface of the substrate before the supplying of the film forming liquid onto the front surface of the substrate from the nozzle is stopped; and removing the cover member from the position facing the front surface of the substrate before the rotating of the substrate at the second rotation speed is completed.
 7. The coating method of claim 1, further comprising: cooling the substrate in the period during which the film forming liquid is supplied onto the front surface of the substrate from the nozzle; and stopping the cooling of the substrate before the rotating of the substrate at the second rotation speed is stopped.
 8. The coating method of claim 7, wherein the stopping of the cooling of the substrate is performed at a timing which is set to allow a period between the timing and a time point when the supplying of the film forming liquid onto the front surface of the substrate from the nozzle is stopped to be shorter than a period between the timing and a time point when the rotating of the substrate at the second rotation speed is completed.
 9. The coating method of claim 7, wherein, when the rotating of the substrate is performed, the substrate is rotated while being held by a rotating holder from a rear surface side of the substrate, and when the cooling of the substrate is performed, an annular region of the substrate at an outer side than a region of the substrate held by the rotating holder is cooled.
 10. The coating method of claim 7, wherein a cooling liquid is supplied onto a rear surface of the substrate when the cooling of the substrate is performed.
 11. A coating apparatus, comprising: a liquid supply equipped with a nozzle configured to discharge a film forming liquid; a rotating holder configured to hold and rotate a substrate; a liquid supply controller configured to control the liquid supply to supply the film forming liquid to a center of a front surface of the substrate from the nozzle in a state that a distance between the front surface of the substrate and the nozzle is maintained at a coating distance; and a rotation controller configured to rotate the substrate at a first rotation speed around an axis, which passes through the center of the front surface of the substrate, in a period during which the film forming liquid is supplied onto the front surface of the substrate from the nozzle, to allow the film forming liquid to be diffused to an edge of the substrate from an outer periphery of the nozzle by a centrifugal force; and rotate the substrate around the axis at a second rotation speed after the supply of the film forming liquid onto the front surface of the substrate from the nozzle is stopped, to allow the film forming liquid to be further diffused by a centrifugal force, and wherein the coating distance is set to allow the film forming liquid to be kept between the nozzle and the front surface of the substrate when the discharge of the film forming liquid from the nozzle is stopped.
 12. A computer-readable recording medium having stored thereon computer-executable instructions that, in response to execution, cause an apparatus to perform a coating method as claimed in claim
 1. 